import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
//        E.right = H;
        return A;

    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root==null){
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);

    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }


    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null){
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root == null){
            return 0;
        }
        return size2(root.left) + size2(root.right)+1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root == null){
            return;
        }
        if(root.left == null && root.right == null){
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if(root == null){
            return 0;
        }
        if(root.left == null && root.right == null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        return 0;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root == null){
            return 0;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return Math.max(leftHeight,rightHeight)+1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root == null){
            return null;
        }
        if(root.val == val){
            return root;
        }
     TreeNode leftNode =    find(root.left,val);
        if(leftNode != null){
            return leftNode;
        }

       TreeNode rightNode =  find(root.right,val);
        if(rightNode != null){
            return rightNode;
        }
        return null;

    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root == null){
            return;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode cur = queue.poll();
            System.out.print(cur.val+" ");
            if(cur.left != null){
                queue.offer(cur.left);
            }
            if(cur.right != null){
                queue.offer(cur.right);
            }
        }
        
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null){
            return  true;
        }
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while( !queue.isEmpty()&& queue.peek() != null){
            TreeNode cur = queue.poll();
            queue.offer(cur.left);
            queue.offer(cur.right);
        }
    while(! queue.isEmpty()){
        TreeNode cur = queue.poll();
        if(cur!=null){
            return false;
        }
    }
    return true;
    }

    /**
     * 最近公共祖先
     *
     * @param root
     * @param p
     * @param q
     * @return
     */
    //1. p|q == root,返回root
    //2. p| q ,在root的两侧 :返回root
    // p , q 在root 的一侧
    //递归的时候,看左子树|| 右子树看成一棵树对待
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if(root == null) {
            return  null;
        }
        if(p == root || q == root){
            return root;
        }
        TreeNode leftN  = lowestCommonAncestor(root.left,p,q);
        TreeNode rightN  = lowestCommonAncestor(root.right ,p,q);
        if(leftN != null && rightN != null){
            return root;
        }else if(leftN!=null && rightN ==null){
            return leftN;
        }else if(leftN==null && rightN !=null){
            return rightN;
        }else{
            return null;
        }

    }
    public int i;
    public TreeNode buildTree(char[] preorder, char[] inorder) {
        return buildTreeChild(preorder, inorder,0,inorder.length-1 );
    }
    public TreeNode buildTreeChild(char[] preorder ,char[] inorder, int begin,int end){
        if(begin>end){
            return null;
        }
        int index = find(inorder ,preorder[i] ,  begin,end);
        TreeNode root = new TreeNode(preorder[i]);
        i++;
     root.left = buildTreeChild(preorder,inorder,0 , index -1);
     root.right = buildTreeChild(preorder,inorder,index+1,inorder.length-1);
     return root;

    }
    public int find(char[] inorder, char val,int begin ,int end ){
        for (int j = begin; j <= end ; j++) {
            if(inorder[j] == val){
                return j;
            }
        }
        return -1;
    }

}